Search USGS⌕ Search

SEARCH · Search USGS

Results for “Topographic Map”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
USGS2001

Digital geologic map of the Fawnskin 7.5' quadrangle, San Bernardino County, California

Version 1.1 of this Open-File Report contains a digital geologic map and map database of the Fawnskin 7.5' quadrangle, San Bernardino County, California, that includes: 1. ARC/INFO (Environmental Systems Research Institute) version 7.2.1 double-precision coverages of the various elements of the geologic map 2. A PostScript (.ps) file to plot the geologic map on a topographic base, containing a Correlation of Map Units diagram and a Description of Map Units 3. Portable Document Format (.pdf) files of: a. This Readme; includes in Appendix I, data contained in fskn_met.txt b. The same graphic as plotted in 2 above. (Test plots from this .pdf do not produce 1:24,000-scale maps. Adobe Acrobat page-size settings control map scale.) This release includes features not found in most other digital geologic maps, in that all polygons, lines, and points in the coverage are encoded with detailed, comprehensive geologic data contained in six INFO data tables (.rel). (See Matti and others, 1998a, 1998b, and 1998c, for information on how the encoding may be accessed and utilized.) No paper map is included in the Open-File Report, but a PostScript plot file containing an image of the geologic map sheet, topographic base, Correlation of Map Units (CMU), and detailed Description of Map Units (DMU) is. The Correlation of Map Units and Description of Map Units are in the editorial format of USGS Miscellaneous Investigations Series maps (I-maps) but have not been edited to comply with I-map standards. Within the geologic map data package, map units are identified by such standard geologic-map criteria as formation name, age, and lithology. Even though this is an author-prepared report, every attempt has been made to closely adhere to the stratigraphic nomenclature of the U.S. Geological Survey. Descriptions of units can be obtained by viewing or plotting the .pdf file (3b above) or plotting the PostScript file (2 above). If roads in some areas, especially roads that parallel topographic contours, do not show well on plots of the geologic map, we recommend use of the USGS Fawnskin 7.5' topographic quadrangle in conjunction with the geologic map.

California↗
USGS2013

The role of photogeologic mapping in traverse planning: Lessons from DRATS 2010 activities

We produced a 1:24,000 scale photogeologic map of the Desert Research and Technology Studies (DRATS) 2010 simulated lunar mission traverse area and surrounding environments located within the northeastern part of the San Francisco Volcanic Field (SFVF), north-central Arizona. To mimic an exploratory mission, we approached the region “blindly” by rejecting prior knowledge or preconceived notions of the regional geologic setting and focused instead only on image and topographic base maps that were intended to be equivalent to pre-cursor mission “orbital returns”. We used photogeologic mapping techniques equivalent to those employed during the construction of modern planetary geologic maps. Based on image and topographic base maps, we identified 4 surficial units (talus, channel, dissected, and plains units), 5 volcanic units (older cone, younger cone, older flow, younger flow, and block field units), and 5 basement units (grey-toned mottled, red-toned platy, red-toned layered, light-toned slabby, and light-toned layered units). Comparison of our remote-based map units with published field-based map units indicates that the two techniques yield pervasively similar results of contrasting detail, with higher accuracies linked to remote-based units that have high topographic relief and tonal contrast relative to adjacent units. We list key scientific questions that remained after photogeologic mapping and prior to DRATS activities and identify 13 specific observations that the crew and science team would need to make in order to address those questions and refine the interpreted geologic context. We translated potential observations into 62 recommended sites for visitation and observation during the mission traverse. The production and use of a mission-specific photogeologic map for DRATS 2010 activities resulted in strategic and tactical recommendations regarding observational context and hypothesis tracking over the course of an exploratory mission.

Acta Astronautica↗
USGS2001

Geologic map of the Lakeview 7.5' quadrangle, Riverside County, California

This Open-File Report contains a digital geologic map and map database of the Lakeview 7.5' quadrangle, Riverside County, California, that includes: 1. ARC/INFO (Environmental Systems Research Institute) version 7.2.1 double-precision coverages of the various elements of the geologic map 2. A Postscript file to plot the geologic map on a topographic base, and containing a Correlation of Map Units diagram and a Description of Map Units 3. Portable Document Format (.pdf) files of: a. This Readme; includes, in Appendix I, data contained in lkvw_met.txt b. The same graphic as plotted in 2 above. (Test plots from this .pdf do not produce 1:24,000-scale maps. Adobe Acrobat page size settings control map scale.) This release includes features not found in most other digital geologic maps, in that all polygons, lines, and points in the coverage are encoded with detailed, comprehensive, contained in five INFO data tables (.rel) (see Matti and others, 1998a, 1998b, and 1998c for information on how the encoding may be accessed and utilized). No paper map is included in this report, but a PostScript plot file containing an image of the geologic map sheet, topographic base, Correlation of Map Units (CMU), and detailed Description of Map Units (DMU) is. Within the geologic map data package, map units are identified by standard geologic map criteria such as formation name, age, and lithology. Even though this is an author-prepared report, every attempt has been made to closely adhere to the stratigraphic nomenclature of the U. S. Geological Survey. Descriptions of units can be obtained by viewing or plotting the .pdf file (3b above) or plotting the postscript file (2 above). If roads in some areas, especially roads that parallel topographic contours, do not show well on plots of the geologic map, we recommend use of the USGS Lakeview 7.5' topographic quadrangle in conjunction with the geologic map.

California↗
USGS1983

Magnetic models of crystalline terrane; accounting for the effect of topography

Igneous rocks commonly have large magnetic susceptibilities so that high topographic relief in crystalline terrane can produce significant anomalies in aeromagnetic surveys. Topographic anomalies are particularly significant in relatively undeformed volcanic terrane because young volcanic rocks generally have large natural remanent magnetizations as well as large susceptibilities. These anomalies commonly appear in aeromagnetic surveys as a complex pattern of high-amplitude, short-wavelength magnetic features that tend to obscure anomalies caused by deeper geologic sources. We have facilitated geologic interpretation of an aeromagnetic survey of the Oregon Cascade Range by calculating the magnetic field caused by a three-dimensional (3-D) topographic model. Maps of the calculated field are compared with observed aeromagnetic data both visually and with a numerical technique that produces a contour map of correlation coefficients for the model. These comparisons allow quick recognition of anomalies caused by normally or reversely magnetized topographic features and, more importantly, identification of anomalies caused by geologic features not obviously caused by the topography.

Oergon↗
USGS1982

Map projections used by the U.S. Geological Survey

After decades of using only one map projection, the Polyconic, for its mapping program, the U.S. Geological Survey (USGS) now uses sixteen of the more comnon map projections for its published maps. For larger scale maps, including topographic quadrangles and the State Base Map Series, conformal projections such as the Transverse Mercator and the Lambert Conformal Conic are used. On these, the shapes of small areas are shown correctly, but scale is correct only along one or two lines. Equal-area projections, especially the Albers Equal-Area Conic, and equidistant projections which have correct scale along many lines appear in the National Atlas. Other projections, such as the Miller Cylindrical and the Van der Grinten, are chosen occasionally for convenience, sometimes making use of existing base maps prepared by others. Some projections treat the Earth only as a sphere, others as either ellipsoid or sphere. The USGS has also conceived and designed several new projections, icluding the Space Oblique Mercator, the first map projection designed to permit mapping of the Earth continuously from a satellite with low distortion. The mapping of extraterrestrial bodies has resulted in the use of standard projections in completely new settings. With increased computerization, it is important to realize that rectangular coordinates for all these projections may be mathematically calculated with formulas which would have seemed too complicated in the past, but which now may be programed routinely, if clearly delineated with numerical examples. A discussion of appearance, usage, and history is given together with both forward and inverse equations for each projection involved.

Bulletin↗
USGS2009

Geologic Map of the Carlton Quadrangle, Yamhill County, Oregon

The Carlton, Oregon, 7.5-minute quadrangle is located in northwestern Oregon, about 35 miles (57 km) southwest of Portland. It encompasses the towns of Yamhill and Carlton in the northwestern Willamette Valley and extends into the eastern flank of the Oregon Coast Range. The Carlton quadrangle is one of several dozen quadrangles being mapped by the U.S. Geological Survey (USGS) and the Oregon Department of Geology and Mineral Industries (DOGAMI) to provide a framework for earthquake- hazard assessments in the greater Portland, Oregon, metropolitan area. The focus of USGS mapping is on the structural setting of the northern Willamette Valley and its relation to the Coast Range uplift. Mapping was done in collaboration with soil scientists from the National Resource Conservation Service, and the distribution of geologic units is refined over earlier regional mapping (Schlicker and Deacon, 1967). Geologic mapping was done on 7.5-minute topographic base maps and digitized in ArcGIS to produce ArcGIS geodatabases and PDFs of the map and text. The geologic contacts are based on numerous observations and samples collected in 2002 and 2003, National Resource Conservation Service soils maps, and interpretations of 7.5-minute topography. The map was completed before new, high-resolution laser terrain mapping was flown for parts of the northern Willamette Valley in 2008.

Open-File Report↗
USGS2019

Deep convolutional neural networks for map-type classification

Maps are an important medium that enable people to comprehensively understand the configuration of cultural activities and natural elements over different times and places. Although a massive number of maps are available in the digital era, how to effectively and accurately locate and access the desired map on the Internet remains a challenge today. Previous works partially related to map-type classification mainly focused on map comparison and map matching at the local scale. The features derived from local map areas might be insufficient to characterize map content. To facilitate establishing an automatic approach for accessing the needed map, this paper reports our investigation into using deep learning techniques to recognize seven types of map, including topographic, terrain, physical, urban scene, the National Map, 3D, nighttime, orthophoto, and land cover classification. Experimental results show that the state-of-the-art deep convolutional neural networks can support automatic map-type classification. Additionally, the classification accuracy varies according to different map-types. This work can contribute to the implementation of deep learning techniques in the cartographic community and advance the progress of Geographical Artificial Intelligence (GeoAI).

Conference Paper↗
USGS1979

Surficial geology of Pulaski quadrangle, Oswego County, New York

The location and extent of 14 kinds of surficial deposits in Pulaski quadrangle, Oswego County, N.Y., are mapped on a 7.5 minute U.S. Geological Survey topographic quadrangle map. The map was prepared to indicate the lithology and potential for ground-water development at any specific location.

New York↗
USGS2014

The digital global geologic map of Mars: Chronostratigraphic ages, topographic and crater morphologic characteristics, and updated resurfacing history

A new global geologic map of Mars has been completed in a digital, geographic information system (GIS) format using geospatially controlled altimetry and image data sets. The map reconstructs the geologic history of Mars, which includes many new findings collated in the quarter century since the previous, Viking-based global maps were published, as well as other discoveries that were made during the course of the mapping using new data sets. The technical approach enabled consistent and regulated mapping that is appropriate not only for the map's 1:20,000,000 scale but also for its widespread use by diverse audiences. Each geologic unit outcrop includes basic attributes regarding identity, location, area, crater densities, and chronostratigraphic age. In turn, units are grouped by geographic and lithologic types, which provide synoptic global views of material ages and resurfacing character for the Noachian, Hesperian, and Amazonian periods. As a consequence of more precise and better quality topographic and morphologic data and more complete crater-density dating, our statistical comparisons identify significant refinements for how Martian geologic terrains are characterized. Unit groups show trends in mean elevation and slope that relate to geographic occurrence and geologic origin. In comparison with the previous global geologic map series based on Viking data, the new mapping consists of half the number of units due to simpler, more conservative and globally based approaches to discriminating units. In particular, Noachian highland surfaces overall have high percentages of their areas now dated as an epoch older than in the Viking mapping. Minimally eroded (i.e., pristine) impact craters ≥3 km in diameter occur in greater proportion on Hesperian surfaces. This observation contrasts with a deficit of similarly sized craters on heavily cratered and otherwise degraded Noachian terrain as well as on young Amazonian surfaces. We interpret these as reflecting the relatively stronger, lava-rich, yet less-impacted materials making up much of the younger units. Reconstructions of resurfacing of Mars by its eight geologic epochs using the Hartmann and Neukum chronology models indicate high rates of highland resurfacing during the Noachian (peaking at 0.3 km 2 /yr during the Middle Noachian), modest rates of volcanism and transition zone and lowland resurfacing during the Hesperian (∼0.1 km 2 /yr), and low rates of mainly volcanic and polar resurfacing (∼0.01 km 2 /yr) for most of the Amazonian. Apparent resurfacing increased in the Late Amazonian (∼0.03 km 2 /yr), perhaps due to better preservation of this latest record.

Planetary and Space Science↗
USGS2002

Digital version of "Open-File Report 92-181: Geologic map of the Indian Spring quadrangle, San Bernardino County, California"

This is a digital map database version of a previous printed geologic map, U.S. Geological Survey Open-File Report 92–181. The original paper map has been faithfully reproduced as a geologic map database for use in a GIS, and thus does not contain updated geologic information for the map area. This publication consists of three parts: Documentation in the form of a this publication's Open File text, or readme, describing the digital data, how to obtain it, as well as the original map explanation pamphlet. The documentation also consists of FGDC metadata, and a file describing any revisions to the data in this report. All of the documentaion components are available in a variety of file formats. Three Arc/Info (ESRI) formatted coverages of the geologic database, distributed in Arc Interchange (e00) format. The spatial databases in this component of the report consist vector-based GIS datasets that represent geologic contacts, faults, map units, and volcanic vents in the study area, as well as localities of K/Ar samples discussed in the original report, and geologic structure measurements. Plottable map representations of the database at 1:24,000 scale in PostScript and Adobe PDF formats. The plottable files consist of a color geologic map derived from the spatial database, composited with a topographic base map in the form of the USGS Digital Raster Graphic for the map area. Color symbology from each of these datasets is maintained, which can cause plot file sizes to be large.

California↗
USGS2002

Digital version of "Open-File Report 92-183: Geologic map of the Granite Spring Quadrangle, San Bernardino County, California"

This is a digital map database version of a previous printed geologic map, U.S. Geological Survey Open-File Report 92–183. The original paper map has been faithfully reproduced as a geologic map database for use in a GIS, and thus does not contain updated geologic information for the map area. This publication consists of three parts: 1. Documentation in the form of a this publication's Open File text, or readme, describing the digital data, how to obtain it, as well as the original map explanation pamphlet. The documentation also consists of FGDC metadata, and a file describing any revisions to the data in this report. All of the documentaion components are available in a variety of file formats. 2. Three Arc/Info (ESRI) formatted coverages of the geologic database, distributed in Arc Interchange (e00) format. The spatial databases in this component of the report consist vector-based GIS datasets that represent geologic contacts, faults, map units, and volcanic vents in the study area, as well as localities of K/Ar samples discussed in the original report, and geologic structure measurements. 3. Plottable map representations of the database at 1:24,000 scale in PostScript and Adobe PDF formats. The plottable files consist of a color geologic map derived from the spatial database, composited with a topographic base map in the form of the USGS Digital Raster Graphic for the map area. Color symbology from each of these datasets is maintained, which can cause plot file sizes to be large.

California↗
USGS2002

Digital version of "Open-File Report 92-179: Geologic map of the Cow Cove Quadrangle, San Bernardino County, California"

This is a digital map database version of a previous printed geologic map, U.S. Geological Survey Open-File Report 92–179. The original paper map has been faithfully reproduced as a geologic map database for use in a GIS, and thus does not contain updated geologic information for the map area. This publication consists of three parts: 1. Documentation in the form of a this publication's Open File text, or readme, describing the digital data, how to obtain it, as well as the original map explanation pamphlet. The documentation also consists of FGDC metadata, and a file describing any revisions to the data in this report. All of the documentaion components are available in a variety of file formats. 2. Three Arc/Info (ESRI) formatted coverages of the geologic database, distributed in Arc Interchange (e00) format. The spatial databases in this component of the report consist vector-based GIS datasets that represent geologic contacts, faults, map units, and volcanic vents in the study area, as well as localities of K/Ar samples discussed in the original report, and geologic structure measurements. 3. Plottable map representations of the database at 1:24,000 scale in PostScript and Adobe PDF formats. The plottable files consist of a color geologic map derived from the spatial database, composited with a topographic base map in the form of the USGS Digital Raster Graphic for the map area. Color symbology from each of these datasets is maintained, which can cause plot file sizes to be large.

California↗
USGS1919

The oil fields of Allen County, Kentucky, with notes on the oil geology of adjoining counties

This report is based on a reconnaissance investigation of the oil field of Allen County, Ky., which was part of a broader study of the oil and gas fields of Kentucky, Tennessee, and Alabama, on which a general report is planned. Most of the field work was done by Mr. Mather, who spent three and a half weeks in and around the county. Mr. Shaw visited Scottsville, the county seat of Allen County, a few years ago and spent a few days in that vicinity at the beginning of the recent field work, which extended from the middle of April to the middle of May, 1917 He prepared also the first draft of the report and reviewed the literature, including reports in oil and gas journals. The purpose of the field work was to investigate the geology of the county, particularly the structure or lay of the oil-bearing strata and the results of drilling to date. Structural conditions in the producing fields were determined by running level lines to the wells and correlating the data recorded in the well logs generously furnished by the operators. Traverses were made of outcrops, and observations of the dip and strike were made in different parts of the county. Lack of a topographic base map and of time and funds for making an accurate topographic survey render the results of the work somewhat incomplete, but it is hoped they will form a valuable contribution to the knowledge of the geology of this relatively little known region, for little detailed geologic work has been done heretofore within 50 miles of Scottsville. The dips are generally too low to be read by the clinometer, but in some localities unmistakable dips can be observed in extensive outcrops along creek banks and can be measured with a level or hand transit. Few of the beds of this region can be followed any considerable distance, though by means of fossils the stratigraphic position of beds outcropping many miles apart can be determined within a few feet. The black shale is the best horizon marker, but it outcrops in only a few places and is reached in only a few wells outside the oil fields. The field work thus consisted largely in observations on out- , cropping beds in different localities and in estimating the altitude of those identified, in collecting fossils for use in future detailed work, and in obtaining from oil operators data concerning the wells and their output. It included the determination of the general lay of the rocks in the county and surrounding territory and details of structure in certain areas. The rocks lie so nearly flat that without topographic data only the general dip could be made out for a large part of the area examined. A complete set of logs of wildcat wells in the region would have thrown much light on the structure and oil possibilities, but little is known of many of the earlier wells drilled in the region, especially of those altogether unsuccessful. An unsuccessful test is soon forgotten, though the data thus obtained concerning the depth at which different beds were found and the yield of porous strata, whether water, oil, or gas, is of great value to the geologist and oil prospector.

Kentucky↗
USGS1981

Evaluation of radar imagery for geological and cartographic applications

The House/Senate conference report on H.R. 4930 (96th Congress), the Department of the Interior and Related Agencies Appropriations bill, 1980, stated that the U.S. Geological Survey should "begin the use of side-looking airborne radar imagery for topographic and geological mapping, and geological resource surveys in promising areas, particularly Alaska." In response to this mandate, the Survey acquired radar data and began scientific studies to analyze and interpret these data. About 70 percent of the project funding was used to acquire radar imagery and to evaluate Alaskan applications. Results of these studies indicate that radar images have a unique incremental value for certain geologic and cartographic applications but that the images are best suited for use as supplemental information sources or as primary data sources in areas of persistent cloud cover. The value of radar data is greatest for geologic mapping and resource surveys, particularly for mineral and petroleum exploration, where the objective is to locate any single feature or group of features that may control the occurrences of these resources. Radar images are considered by oil and gas companies to be worth the cost of data acquisition within a limited area of active exploration. Radar images also have incremental value for geologic site studies and hazard mapping. The need in these cases is TO inventory all geologic hazards to human life, property, resources, and the environment. For other geologic applications, radar images have a relatively small incremental value over a combination of Landsat images and aerial photographs. The value of radar images for cartographic applications is minimal, except when they are used as a substitute for aerial photographs and topographic maps in persistently cloud-covered areas. If conventional data sources are not available, radar images provide useful information on terrain relief, landforms, drainage patterns, and land cover. Screen less lithography is a low-cost method of reproducing the images. The images from modern, commercially available radar systems have good visual quality; they also have better geometric accuracy and higher information content than images from older systems. Images from modern systems, however, also have some of the same disadvantages as those from older systems. The most serious problem is that considerable information is lost in the process of recording the radar return on film. Another problem is that the oblique radar view of the landscape results in interpretations that are biased by look direction. A compromise antenna depression angle also commonly results in inadequate or excessive shadowing in parts of the image. There is a need for high-resolution digital data, not currently available from the private sector, to significantly improve the utility of radar data for geologic and cartographic applications.

Open-File Report↗
USGS1875

Annual report upon explorations and surveys in the Department of the Platte: Being Appendix QQ of the Annual Report of the Chief of Engineers for 1875

There are at nearly all the headquarters of the tour military divisions and the nine military departments, officers of engineers, whose chief duty it is to collect geographical and other information; and these officers do, by means of their own explorations and surveys, and by collecting the notes, sketches, and maps made by the officers and soldiers belonging to the western posts, in their scouts and campaigns, add much, year by year, to the knowledge of the interior of the country, which is not only essential to the generals in command of these departments and divisions, but useful to the country generally. Capt. W.S. Stanton, on duty with the commanding general of the Department of the Platte, was engaged in the surveys and establishment of the monuments and boundary-lines of the military reservation of Fort Sanders, embracing an area of thirty square miles, pursuant to an act of Congress approved June 9, 1874, the survey of the military reservation of Fort Hartsuff, embracing two townships, and the selection, survey, and examination of the site for a bridge to be built by the United States over the North Platte at Fort Laramie. During the year every post in the department has been supplied with a set of reconnoitering instruments, embracing odometer, prismatic compass, and set of drawing-instruments. Maps and topographical note-books have been issued with instructions, designed to take advantage of every movement of troops to secure geographical and topographical information sufficiently accurate for use in revising and extending the maps of the department. In the Office attention has been given to the collection of information from all sources available. Maps have been made of the reservations surveyed, drawings of the sub-structure for the new bridge over the Platte, and various tracings and numerous sketches have been made. Fifty-four note-books and one hundred and fifty skeleton maps, each containing three degrees of longitude, have been issued for use in connection with movements of troops. Two hundred and thirty maps have been mounted, and two hundred maps have been issued for the use of officers. Four hundred copies of the map of Wyoming Territory, which was constructed by Captain Stanton's predecessor, Capt. W. A. Jones, Corps of Engineers, have been lithographed.

Nebraska, Wyoming↗
USGS1999

Digital geologic map database of the Payette National Forest and vicinity, Idaho

The geology of the Payette National Forest and vicinity, Idaho (Fig. 1), was mapped and compiled by Karen Lund between 1992 and 1996. The geologic data for the digital map are from original mapping as well as compilation by Lund of numerous sources of published and unpublished geologic maps that are cited in the section 'Bibliography of Geologic Map Sources.' The geology was compiled onto 1:100,000-scale topographic base maps for input into a geographic information system (GIS). The digital geologic map database can be queried in many ways to produce a variety of geologic maps. Digital base map data files are not included: they may be obtained from a variety of commercial and government sources. This database is not meant to be used or displayed at any scale larger than 1:100,000 (e.g., 1:62,500 or 1:24,000). This open-file report describes the geologic units and the methods used to convert the geologic map data into a digital format and documents the file structures. We wish to thank Gregory N. Green of the U.S. Geological Survey for reviewing the digital GIS files.

Idaho↗
USGS1971

Prospects for developing stock - Water supplies from wells in northeastern Garfield County, Montana

Ground-water resources in northeastern Garfield County, Mont., afford a practical and reliable source of stock water on the intermingled public and private grazing lands that together comprise an area of about 1,200 square miles. The oldest formation exposed in the area is the relatively thick and impermeable Bearpaw Shale of Cretaceous .age. Overlying the Bearpaw Shale in succession are the Fox Hills Sandstone and Hell Creek Formation of Cretaceous age, the Fort Union Formation of Tertiary age, and thin glacial deposits .and alluvium of Quaternary age. All but the Bearpaw Shale and the glacial deposits are potential aquifers. Published geologic maps were found to be satisfactory after fitting contacts to the topographic base. Mapping, therefore, was limited mainly to outlining on aerial photographs the alluvial deposits in the stream valleys. The major structural feature is the Blood Creek syncline, the axis of which plunges eastward 10-15 feet per mile across the southern part of the area. Beds generally dip 15-25 feet per mile toward the synclinal axis. Water in bedrock aquifers is under artesian pressure, .and most wells in Big and Little Dry Creek valleys flow at the land surface. The only bedrock aquifer having appreciable areal extent is a sandstone 30-70 feet thick that has been mapped by previous investigators as the upper part of the Fox Hills Sandstone. This aquifer crops out in the northern and northwestern parts of the area and dips about 20 feet per mile southeastward beneath younger beds. Most wells in the northern half of the area obtain water from this sandstone at drilling depths of less than 200 feet. The depth to the Fox Hills Sandstone increases progressively southward, and most wells south of Woody Creek obtain water from irregularly distributed sandstone beds and lenses in the overlying Hell Creek and Fort Union Formations. The depth at which water may be obtained from these beds is not accurately predictable, but the depth seldom exceeds 300 feet. The results of the investigation indicate that the prospects for obtaining ample water for livestock from wells drilled into the bedrock formations are very favorable in most of the area. The average depth of bedrock wells in the area is 195 feet. Underflow in the alluvial deposits along all the larger stream valleys also affords a practical source of stock water. Chemical analyses of samples collected at 43 wells and three springs show the water quality to be generally poor. Water from bedrock aquifer contains 530-5,340 milligrams per liter total dissolved solids, whereas water from alluvium contains less than 1,500 milligrams per liter total dissolved solids. The predominant constituents are sodium, bicarbonate, and sulfate. So far as could be determined, all water supplies in the area are suitable for livestock.

Montana↗